Conventionally, there is known a technique of reforming natural gas and water vapor in a catalyst. For example, in Patent Reference-1, there is disclosed a technique of making methane (CH4) react with water vapor (H2O) and converting them into the reformed fuel consisting of carbon monoxide (CO) and hydrogen (H2). In Patent Reference-2, there is disclosed a technique of supplying the engine with gas fuel in a case where the temperature of the engine at the time of the start thereof is lower than a predetermined threshold.
Patent Reference-1: Japanese Patent Application Laid-open under No. 2005-030243
Patent Reference-2: Japanese Patent Application Laid-open under No. 2008-169704